1. Field of the Invention
The present invention relates to a detecting system and a method for estimating the loading and height of a vehicle.
2. Technical Background
There are various types of conventional height-estimators for vehicles currently being used in order to improve the control of the wheel-suspension of a vehicle and thus the driving comfort. One estimator type, preferably connected between a sprung and an unsprung part of a vehicle, has a hinged arm with position sensors. Depending on the loading of the vehicle the connected hinged arm of the installed estimator will assume a certain position for a given distance and the distance detected by the prior art estimator is increased or decreased. This estimated distance could be used as input data to advanced wheel-suspension control systems and the like.
The position between e.g. the body and the wheel suspension of a vehicle, where the estimator is preferably placed, experiences rough conditions, especially during driving in mud, snow, ice etc. and also mechanical wear. The height-estimating device of the above-described type is sensitive to these kinds of conditions due to the fact that the hinged arm cannot be fully protected from these conditions. This, of course, may affect the functionality of the hinged arm and the sensors, especially in severe conditions.
Another issue of the above described height-estimating device is that it is difficult to install and calibrate the device correctly in relation to other height-estimating devices of the vehicle. Not only is the position between the body and the wheel-suspension difficult to access for a mechanic during manufacturing of the vehicle, it is also difficult to maintain the precision of the system during use of the vehicle due to the sensitivity of the arm to outer influence.
The object of the present invention is to provide a reliable system that overcomes the above issues, and makes it possible to provide a detecting system for estimating the loading and height of a vehicle. A further object of the present invention is to provide an accurate and precise method for estimating the loading and height of a vehicle.
It is still a further object to provide a detecting system that is easy to install in a vehicle and can withstand tough conditions.
According to the invention there is provided a detecting system for detecting the loading of a vehicle, wherein the detecting system comprises at least one accelerometer in a first position and arranged in a predefined direction on said vehicle, wherein the acceleration of gravity in said predefined direction may be used as a reference value for the accelerometer and said accelerometer is arranged to detect the deviation of acceleration relative to said first position, said deviation being related to the loading of said vehicle. This system provides a load detecting system comprising at least one accelerometer that is easy to install. The first position and direction of the accelerometer on the vehicle can conveniently be established after the installation using the acceleration of gravity as reference value. Further, the accelerometer does not need any outer movable parts and can be fitted in a cover. The cover is preferably adapted to a desired position on the vehicle.
In an embodiment of the invention the detected change in vertical acceleration relative to said first position is related to an angular displacement of the accelerometer from said first position, relative to a point, caused by the displacement of a vehicle due to the actual loading.
This arrangement provides a possibility of detecting the loading or height of a vehicle by using the relation of how loading affects the angle of a sprung part of the vehicle. Preferably the accelerometer is arranged fixedly in relation to a hub of said vehicle and the change in camber and/or caster is detected. In a preferred embodiment the accelerometer is installed on a shaft of a spindle. Depending on the type of shaft the camber readings can be taken into account. In an alternative embodiment the accelerometer is arranged on a shaft where the caster readings are to be taken into account. It is understood that an accelerometer of the inventive load detecting system placed at every wheel of a vehicle provides a more accurate reading of the loading to which every wheel is exposed.
Preferably the accelerometer is a capacitive accelerometer that makes it possible to detect static as well as dynamic loading of said vehicle. The load detecting system can also be used for determination of the dynamic camber on a vehicle tire, performed while the tire is moving along an actual road surface and mounted on an actual vehicle of the type on which the tire will be used, which data can then be used in order to test various modifications and changes to a tire in a test facility, in order to arrive at the optimum tire design for a particular vehicle.
In a further preferred embodiment of the invention the detecting system is connected to a system of level detectors arranged on the vehicle body.
This arrangement makes it possible to establish how the vehicle is positioned relative to the normal horizontal plane so that e.g. the effects of a wheel on a curb or the vehicle being parked on a steep slope do not lead to miscalculations of the load distribution of the vehicle.
The detecting system is preferably connected to a control unit in order to control the springing and damping behavior of said vehicle. For this purpose the detecting system according to a preferred embodiment of the invention is connected to a spring and damper system of said vehicle. This arrangement makes it possible to detect the road clearance. In situations where the clearance is insufficient due to e.g. heavy carrying load or the fact that the vehicle passes an uneven spot on the road the spring and damper system of the vehicle can be activated in order to prevent damage.
These objects and advantages are further achieved by the method of the present invention for detecting the loading of a vehicle, wherein the method comprises the following steps: arranging at least one accelerometer in a first position and in a predefined direction on said vehicle, using the acceleration of gravity in said predefined direction as a reference value for the accelerometer, and using said accelerometer for detecting the deviation of vertical acceleration relative to said first position, said deviation being related to the loading of said vehicle.
In a further preferred embodiment of the present invention the method comprises the step of combining said detecting system with a system of vehicle body level detectors, for identifying a reference level from which the deviation depending on the actual loading of said vehicle may be identified by said detecting system. This method makes it possible to establish how the vehicle is positioned relative to the normal horizontal plane so that e.g. the effects of a wheel on a curb or the vehicle being parked on a steep slope do not lead to an erroneous detection of the load distribution of the vehicle by the accelerometers.